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教学课件
沪外教英语八年级下册
Unit6 语法专项—用since和as给出原因
全解精讲+分层练习
学习目标
1.理解since和as引导原因状语从句的核心定义及表意
2.掌握其两种基本结构及句首使用的标点规则
3.精准辨析since/as与because的区别，规避使用错误
4.熟记since和as的互换规则、时态一致原则
5.能灵活运用知识点完成各类题型解题，贴合主题写作
语法核心定义
since / as 可引导原因状语从句，表“既然；因为”
核心语义：补充说明已知/显而易见的原因
语气特点：比because弱，更偏向书面化表达
使用场景：贴合论述、演讲类语境，本单元侧重语言主题
基本结构1 原因从句放主句后
核心公式：主句 + since / as + 原因从句
使用场景：无需强调原因，仅补充说明主句的理由
从句要求：必须是完整的主谓句子
例句：We love language as it connects all the people.
基本结构2 原因从句放句首
核心公式：Since / As + 原因从句, + 主句
关键规则：从句放句首时，后必须加逗号分隔主句
使用场景：强调已知前提，让原因更突出
例句：Since language is powerful, we should use it well.
基本结构 例句对比解析
1.从句后置：We should practise speaking since it improves skills.
译：我们应该练习口语，因为这能提升技能。
2.从句前置：As it improves skills, we should practise speaking.
译：既然这能提升技能，我们应该练习口语。
核心：位置不同，表意一致，标点随位置变化
小练习 补全句子结构
根据结构要求，补全下列句子
1.We should respect all languages ____________ they carry culture.
2.____________ everyone can speak, we should listen to others carefully.
3.Language shapes thoughts ____________ it influences our thinking way.
since/as
Since/As
since/as
核心规则1 since和as可互换
核心原则：表原因时，二者语义、用法完全一致
可直接替换，不改变句子意思，标点规则不变
例句1：As the speech is important, we need to prepare well.
例句2：Since the speech is important, we need to prepare well.
核心规则2 时态一致原则
核心要求：主句和since/as引导的从句时态必须统一
现在时搭配：It is useful as it helps our daily communication.
过去时搭配：He made the speech since he wanted to encourage people.
无跨时态使用情况，前后时态保持对应
小练习 时态匹配填空
根据主句时态，补全从句动词形式
1.Since he _________ (be) good at speaking, he gives the speech.
2.We valued the language as it _________ (carry) our culture.
3.As they _________ (practise) hard, they speak English well.
is
carried
practise
核心考点 since/as vs because 对比（一）
对比维度 since / as because
语气强度 较弱，轻描淡写已知原因 较强，强调核心、直接原因
回答问题 不能回答Why引导的特殊疑问句 可直接回答Why引导的问句
核心考点 since/as vs because 对比（二）
对比维度 since / as because
用法场景 书面表达、论述、演讲，正式文体 日常对话、普通写作，口语化
位置特点 可句首/句后，句首加逗号 可句首/句后，句首加逗号
引导词对比 例句解析
since/as（书面，补充已知原因）
Since time is limited, we should finish the speech quickly.
because（口语，强调核心原因，可答Why）
—Why do you finish quickly —Because time is limited.
同义替换
We should finish quickly because time is limited. = We should finish quickly since time is limited.
小练习 选since/as/because填空
1._________ you know the reason, I won’t say it again.
2.—Why do you learn English —_________ it is useful for communication.
3.We should use words carefully __________ they shape our relationships.
.Since/As
Because
since/as
拓展 与for的用法区分
since/as：可句首/句后，表已知原因，无逗号要求（句首除外）
Since it is late, we go home. / We go home since it is late.
for：只能句后，前加逗号，表补充说明的原因
We go home, for it is late.
核心：位置和标点是最直观区分点
语法小测 判断正误
判断下列句子正误，标注错误原因
1.Since it is raining, we stay at home.
2.We love reading as it is interesting.
3.As he is ill so he doesn’t go to school.
4.Since you know, why do you ask me
√
√
× 去掉so
√
语法小结 核心框架（一）
1.两种结构：从句后置（主句+since/as+从句）；从句前置（Since/As+从句,+主句）
2.两大规则：since和as可互换；主从句时态必须一致
3.标点要求：从句放句首时，后必须加逗号，后置无逗号
4.核心语义：表已知、显而易见的原因，语气较委婉
语法小结 核心框架（二）
1.与because区别：语气更弱、书面化，不能回答Why问句
2.与for区别：位置不同（可句首）、标点不同（后置无逗号）
3.使用场景：书面论述、演讲、语言/文化类主题写作
4.易错点：从句句首忘加逗号；主从句时态不一致
单项选择
1.We should learn new words ________ it helps us understand different cultures.
A. since B. because of C. but D. so
2.______ language is a bridge, we should build it well.
A. Since B. Because of C. So D. Or
3.The speech touched people ________ it was full of love and hope.
A. since B. because C. A and B D. none
4.We need to listen carefully ________ everyone has something to say.
A. as B. because of C. but D. and
5.______ he practises speaking every day, he speaks English fluently.
A. As B. Because of C. So D. For
A
A
C
A
A
6.Loanwords are important ________ they connect different languages.
A. since B. because C. A and B D. but
7.We should choose words well ________ they influence others’ feelings.
A. as B. because of C. so D. yet
8.______ the story is moving, people remember it for a long time.
A. Since B. Because of C. But D. So
9.He is good at speaking ________ he talks with foreigners often.
A. as B. because C. A and B D. but
10.We study grammar ________ it helps us use language correctly.
A. since B. because of C. but D. so
C
A
A
C
A
用since/as合并句子
1.English is popular. It is used in many countries.
2.We should practise writing. It improves our language skills.
3.The book is meaningful. It tells us the power of words.
4.Everyone can express themselves. We should respect others’ words.
5.She is good at English. She learns it every day.
English is popular since/as it is used in many countries.
Since/as we need to improve our language skills, we should practise writing.
The book is meaningful as/since it tells us the power of words.
Since/as everyone can express themselves, we should respect others’ words.
She is good at English since/as she learns it every day.
短文填空（since/as/because）
Language is one of the greatest inventions of humans. 1.____________ it is very important, we should learn to use it well. We learn English 2._________ it is an international language. 3.____________ everyone can speak, we should listen to others patiently. People love stories 4.___________ they are full of feelings and thoughts. 5.____________ words can shape the world, we should choose them carefully.
Since/As
since/as/because
Since/As
since/as/because
Since/As
根据中文意思，用since/as完成句子
1.既然语言承载文化，我们就应该尊重它。
___________ language carries culture, we should respect it.
2.我们应该多读书，因为这能丰富我们的知识。
We should read more books ____________ it can enrich our knowledge.
3.既然每个人都有表达的权利，我们就应该认真倾听。
___________ everyone has the right to express, we should listen carefully.
Since/As
since/as
Since/As
课堂总结 核心知识点回顾
1.since/as表“既然/因为”，引导原因状语从句，可互换、时态一致
2.两种结构：从句后置无逗号，从句前置加逗号，标点是关键
3.与because比：语气更弱、书面化，不能回答Why引导的问句
4.使用场景：书面论述、演讲，贴合语言/文化类主题写作
课堂总结 高频易错点梳理
1.从句放句首时，忘记在从句后加逗号，这是核心易错点
2.混淆since/as与because of，后者后接名词，不可接句子
3.主从句时态不一致，忽略现在时/过去时的对应搭配
4.多余使用连词，如As it is late, so we go home.
教学课件
Unit6 语法专项—用since和as给出原因
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